During seek operations, embedded servo information is read from tracks as the read/write head rapidly transverses a number of the tracks. The head movement causes a timing offset between radially adjacent servo tracks called “radial incoherence.” Radial incoherence results in phase shift that can be as high as, for example, one clock period after 50 clock periods. Errors in reading the embedded servo information can occur due to increasing phase difference between servo data being read and a demodulator clock as shown in FIG. 5. Known algorithms for dealing with radial incoherence have suboptimal performance in systems with noise, non-linearity and distortion. An algorithm is needed to provide an improved combination of signal to noise ratio and detection probability.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.